In commerce and industry today, the useful life of corrodible items may be extended and/or preserved by providing corrosion inhibitors which protect the corrodible item from the adverse effects of its ambient environment. Materials which are of concern for their corrosive properties include gases such as oxygen, water vapor, sulfides, carbon dioxide, aqueous aerosols containing salts or acids, and the like. Among the common indications of corrosion manifested in useful metallic articles are oxidation, pitting, tarnishing, mottling, or surface discoloration. Metals which are frequently found to be susceptible to corrosion under normal atmospheric and ambient conditions are iron, copper, brass, aluminum, silver, and alloys of these metals. Corrosion of steel is of particular economic significance due to the extensive use of steel in transportation vehicles, buildings, tanks and pipelines, industrial equipment, and transportation infrastructure (roads, bridges, etc.). Corrosion inhibitors have been found useful in protecting certain corrodible items against reaction with corrosive environmental factors, which, in the absence of corrosion inhibitors, cause reduction in effectiveness, useful life, and value. Such protection may be needed during packaging, handling, shipment, or end use.
In the past, it has been known to provide a package or other enclosure containing one or more inhibiting compounds along with the corrodible item or items to be protected. Additionally, articles have been protected from corrosion by means of protective coatings in the form of solids, liquids, greases, or pastes.
Steel is often processed at elevated temperatures for forming into sheets or rods, wires, or tubes/pipes. At these elevated temperatures, oxides/scale commonly forms on the surface. Such surface scale is undesirable in the final article and is usually removed by cleaning or pickling in an aqueous acid bath. Hydrochloric acid (HCl) is most commonly used to surface treat carbon steel products. Roughly 55 percent of all steel mill products are pickled. The hydrochloric acid preferentially reacts with oxide and scale, but also dissolves to some extent the steel itself. For this reason, corrosion inhibitors are added to pickling baths. After such surface cleaning, the steel can be very susceptible to reformation of rust (flash corrosion), particularly if the steel is stored for an extended period of time. It is therefore desirable for the corrosion inhibitor used in the cleaning process to provide residual protection to the steel.
A related but less demanding application is the acid cleaning of steel to remove surface rust and/or mineral precipitates (e.g. calcium salts) from processing equipment and/or steel pieces/articles. Such cleaning is typically done at lower temperatures and lower acid concentrations than for pickling, but it is still very important to prevent steel loss and reformation of surface oxides after treatment. The products used in such applications are the same or similar to those used with pickling, but vary somewhat in formulation depending on the strength and type of acid used.
Current corrosion inhibitor products are proven and effective, but they tend to be expensive. Further, some of the cleaning materials may be toxic (inhalation and skin contact risk), flammable, and pose environmental risks. There is accordingly a need for safer and more environmentally friendly corrosion inhibiting products that are also cost effective.